This invention is directed to the protection of articles and devices that are normally subject to oxidative degradation and/or vandalism damage. It is common for the devices being protected according to this invention to be used out of doors. Examples of such devices are parking meters, traffic signs, toll collection baskets, and the like. Some conventional, oxidation sensitive devices are used indoors or out. Examples of these devices are vending machines, public telephones, and the like. This invention is directed to the protection of any or all of these types of apparatus that are intended to reside in public, or quasi-public, areas, such as on the street, in hallways, etc. The invention is also applicable to protect elements (that is less than the whole of the device) of devices that are subject to vandalism or oxidative degradation and/or humidity damage, even where the whole of the device has certain elements that are not subject to such damage.
While at the present time, most, if not all, of the devices to which the protection of this invention is directed are coin or card operated, in the future, many of these coin and/or card operating devices will be replaced by, or modified to accept, wireless communication, such as from a cell phone or the like. In fact, currently, such cradless and coinless operated outdoor equipment is already in the form of xe2x80x9cSPEEDPASSxe2x80x9d, the operator of gasoline dispensing apparatus that is marketed by Mobil Oil. It is also used to charge the payment of tolls to the driver""s credit card.
This invention is directed to all such outdoor, oxidation and/or vandalism sensitive, devices regardless of how they are activated or initiated. It more particularly is directed to improving the resistance of such devices to environmental damage as well as resisting damage due to intentional vandalism or accidental collision. While this invention is applicable to such outdoor devices regardless of their chemical composition, it is most efficiently protective of such devices that are made up least partially of oxidation sensitive ferrous metals and zinc based structure.
For ease of understanding and explanation, parking meters, and structural elements thereof, will hereafter be used as illustrative of all of the oxygen, humidity and vandalism sensitive devices to which this invention is directed. The use of such illustrative elements in this specification is not intended to be limiting on the scope of the instant invention, but rather should be taken as a convenient short hand method of defining and describing this invention.
Parking meters, vending machines, public telephones and the like, comprised in whole or in part of oxidation sensitive ferrous metal, or other oxidation sensitive material, are well known to be subject to damage through environmental deterioration because of rusting, crazing, cracking, pitting and the like. All devices that are generally available to the public are routinely subject to abuse by reason of vandalism or accidental collision. It is well known that outdoor devices are often scratched or dented because of malicious mischief or as a result of just plain accidental encounters, for example by reason of an automobile running into a parking meter or a gasoline pump of a toll collection basket, etc. The readily oxidizable ferrous metal parts of a device, even if they are intended for use inside a structure and not out doors, are still subject to environmental deterioration since the devices are not usually hermetically sealed. In any case, possible damage because of vandalism can always be a problem that needs to be addressed.
The art is replete with means for preventing, or at least reducing, the impact of, such damage by applying coatings made of various compositions at least to exposed ferrous metal members of the outdoor devices. One very common protective method is to galvanize ferrous metal parts, i.e. by applying a zinc based coating thereon followed by conventional galvanizing. Galvanizing certainly assists in preventing or at least retarding corrosive action of the environment and thereby increases the life of ferrous metal parts that have been galvanized. However, galvanizing is not the ultimate protection. It is intended that parking meters be left in place for a very long time, on the order to 50 years. Clearly, their protection must be more than minimal.
It is well known to apply oxidation and scratch resistant polymeric coatings over both the oxidizable ferrous metal and other structural elements of outdoor devices in order to protect them from damage. These polymeric coatings can be applied directly to the metal, e.g. coating directly on oxidizable ferrous metal surfaces, or they can be applied over an intermediate coating layer of some other composition, for example on top of a zinc galvanizing layer. Multiple polymeric layers are also generally known, although these have not been applied to parking meters and the like. In addition to polymeric coatings that can be applied by brushing, spraying or otherwise, it is known to apply suitable coatings over devices or parts thereof by the use of so-called powder application. Both cationic as well as anionic electrocoating application of polymeric coatings, such as specially formulated paint, is a well known method employed in the automobile industry to coat parts of cars that are not readily accessible, such as the inside of rocker panels. Both cationic and anionic electrocoating techniques are generally well known.
Powder coating is carried out by depositing an appropriately formulated powder on the part being coated, applying a d.c. electrostatic charge of opposite polarity to the powder and the substrate, respectively, heating the powder, suitably through the substrate especially if it is a good heat conductor, sufficient to melt the powder and to cause it to flow and spread out to cover the substrate to a film thickness that prevents, or at least substantially reduces, the advent of pinholes or surface cracks and crazing in the resultant coating, and, after the powder has become a substantially continuous coating, cooling the coated substrate and thereby solidifying the coating and adhering it to the substrate. The object here is to provide a coating that is of minimal thickness sufficient to insure substantially complete coverage that will resist environmental attack on the surface portions of the substrate that would otherwise be exposed to the atmosphere, and to resist or at least ameliorate the adverse effects of vandalism or accidental collision. Further, the coating should be of a tough material that tends to prevent penetration by sharp objects such as a knife or a nail, and preferably of a material that tends to self heal. The tougher the coating material is, the thinner it can be in order to provide good protection. Thus, the coating should have a minimal thickness sufficient to substantially prevent, collision, malicious scratching or atmospheric attack. In general, non-epoxy, meltable polymer coating compositions, such as those set forth in the above identified parent application, are suitable for this use. They are conveniently applied as a powder and converted into a thin protective thermosetting polymer film by the above described process.
Certain applicable prior art is disclosed in the parent application/patent, and such disclosure is incorporated herein by reference. The parent application/patent also discloses very effective coatings for ferrous metal parts that are intended for use in an outdoor environment. These coatings comprise multiple layers including: a hot dipped zinc intermediate layer, covered by an electrostatically applied non-epoxy, organic, electrically insulating thermosetting layer that had been applied by a powder coating method. This improved product has been found to be an excellent preventor of environmental and other damage. However, as with all things, improvements are to be desired.
One important object of this invention is to provide an improved coating for protection of oxidizable metal substrates, particularly ferrous metal members, or devices that are generally intended for use in contact with the atmosphere, especially outdoors, against environmental and other damage.
Another object of this invention is to provide an improved multi layer coating for protection of oxidizable ferrous metal substrates against environmental damage, such as corrosion.
It is a further object of this invention to provide a novel means of protecting oxadizable metal substrates from all sorts of damage that can be caused by accidental or intentional exposure to the atmosphere and/or vandalism.
Other and additional objects will become apparent from a consideration of this entire specification and the claims appended hereto.
In accord with and fulfilling the above objects, one aspect of this invention comprises a device or other object that is intended to be put into service, and continue to see service over an extended period of time, and that comprises at least one part or member that is subject to oxidation by the ambient atmosphere and that may also be subject to damage as a result of collision or vandalism and that has been protected by application of the multilayer coating of this invention. The device at least partially comprising a member(s) comprising at least one metal that is subject to detrimental attack by ambient atmosphere, such as an oxidizable ferrous metal. It is known to coat such metal member(s) with a succession of protective layers including a zinc primary coating, and then a non-epoxy thermosetting polymeric coating that is suitably applied in a powder form to an electrostatically charged surface to be coated, thereby heating the powder sufficient to cause it to flow over the substrate surface, and forming a coherent protective layer on top of the zinc primer coating. In accord with this invention, the specific nature of the zinc antioxidant layer is not critical. Substantially any anti-oxidation initial coating will be suited to use in this invention and is considered to be within the scope of the appended claims, provided that it adheres tenaciously to the substrate. One particular embodiment of this invention envisions a suitable substrate having thereon, as a first coat, a galvanized zinc primary coating layer, as a second coat, an epoxy free, preferably polyurethane, coating layer, that has preferably been applied by a powder coating, electrostatic technique, and as a top layer, the silicon containing product of curing a suitable composition.
An aspect of the departure of the instant invention from the prior art is to apply as a top coating, an epoxy polysiloxane over the non-epoxy thermosetting polymer. That epoxy polysiloxane top coating is preferably the product of curing a composition comprising: a resin component comprising: at least: an epoxy resin, a polysiloxane, an organooxysilane; a hardener component; and a catalyst component. The top coat layer may also contain a pigment or dye component if the esthetic nature of the final product suggests that a particular color, design or degree of opacity is appropriate. Where appropriate, solid aggregate materials may be incorporated into the top coating composition. These aggregate materials may be simply opacifying agents, such as calcium carbonate for example, or they may be decorative in nature. Incorporation of aggregate materials in the top coating also can tend to reduce damage caused by vandalism, such as scratching, because the aggregate tends to blunt the blade of the vandalizing tool and keep it from going too deep.
One aspect of this invention envisions the repair and reconditioning of outdoor equipment, such as parking meters, that comprise zinc parts or tenaciously adhered zinc layers on oxidizable parts. As part of such reconditioning operation, it is important to remove substantially all of the oxidation products that are present on elements of the equipment in need of refurbishing. This can be done by mechanical means, such as brushing or sand blasting or the like. It can also be done by chemical means such as by treating the equipment with a suitable stripper. Two such chemical strippers are sold commercially by the Oakite Chemical Company, and are catalogued as product Oakite Stripper EPA and Oakite Stripper #156. In this embodiment of this invention, the old equipment can be grossly stripped of oxidation product by mechanical means, and then it can be chemically treated to remove even the small amount of oxidation products that may remain in places that are hard to reach by mechanical means, such as small crevices and tight corners.
Thus, this invention encompasses:
a method of preparing new equipment for outdoor service by applying a multi layer protective coating on surface(s) thereof in need of protection against oxidation, humidity conditions, vandalism or the like;
a method of refurbishing older equipment, to make it capable of continued service, by first removing old coatings and oxidized parts, replacing worn out parts and resizing parts so that they work efficiently in their intended fashion, and then applying a multilayer protective coating; and
the multilayer coated (oxidation and vandalism protected) equipment itself, whether new or refurbished.
One important aspect of the multilayer coating of this invention is the top coat. Reference is here made to U.S. Pat. No. 5,618,860 that discloses a family of compositions that have been found to be exceptionally well suited to use as the top coat layer of the multilayer protective coating of this invention. The entire contents of this ""860 patent are incorporated herein by reference.
In another aspect of this invention, a suitably protected product is constituted of a member in need of protection, a zinc rich substrate either on the member in need of protection, or as the composition of that member; a primary thermosetting polymeric layer, that is preferably not a polyepoxide, and that has preferably been applied electrostatically from a suitably formulated powder, disposed on and adhered to the zinc rich substrate, and an epoxy polysiloxane top layer, that may or may not have dye, pigment or filler therein, applied over, and adhered to, the primary polymeric coating. The thickness of the total coating composition is selected to be as small as practical consistent with the need to protect the underlying structural member against environmental damage and vandalism. It has been found that about 2.5 mils thickness is a suitable minimum. However, it is possible that in some applications, lesser total coating thicknesses may suffice or, in the alternative, some applications may call for greater thicknesses of total protective coating. For example, where the device being protected is in a sheltered environment, such as is common for ATM machines and most vending machines, it may be satisfactory to apply pin-hole free coatings that are only about 2 mils thick. On the other hand, protection for outdoor telephones and their booths, or for parking meters and similar equipment such as ganged parking control as sometimes is found in parking lots, or for toll collecting apparatus, may require greater protective coating thicknesses of about 3 mils or even more in some cases. Further, the thickness of the protective coating of this invention will be a function of the environment to which the device is subjected. Where there are great variations in ambient temperature, the composite of all of the layer(s) may be suitably reduced in total thickness so that crazing and cracking induced by temperature variations will be limited. Where there is a high concentration of salt in the ambient environment, such as in installations that are at or very near the ocean, thicker layers may be required. The overriding consideration in determining the thickness of the protective coating of this invention is that it function against the amount of environmental or vandalism damage (oxidation, salt corrosion, scratching and the like) the device is likely to be subjected to. Further, the thickness is also a function of the toughness or brittleness of the polymeric coating layers. The more brittle the coating, the thinner it must be to avoid cracking and crazing as a function of the temperature and humidity induced expansion and contraction of the coating elements and of the underlying substrate. Thus, the minimum coating thicknesses set forth above should be considered to be exemplary and preferable, but not necessarily limiting on the scope of this invention. It is to be understood that specific thickness of coatings layer(s) will depend on the specific danger that is being protected against.